This is an application for support for a broadly based, interdisciplinary, interdepartmental research program on the physiological basis of pulmonary disease. The chief emphasis is on fundamental aspects of the functions of the lung including mechanisms of blood flow and ventilation, and the relationships between these and pulmonary gas exchange. An important feature of the program is an attempt to relate advances in non-medical departments in a number of areas to problems of pulmonary disease. The 10 principal investigators come from 6 departments including Medicine, Scripps Institution of Oceanography, Applied Mechanics and Engineering Sciences, Mathematics, Anesthesiology, and Pediatrics. Five of the research units are devoted to the mechanisms of blood flow and ventilation in the lung including structure-function relationships of the pulmonary capillaries, hypoxic vasoconstriction of blood vessels, elastic behavior of lung parenchyma, physiology of airways of diving mammals, and turnover of pulmonary surfactant. The five other research units are concerned with gas exchange both in the lung and blood. Projects include distributions of ventilation-perfusion ratios, including theoretical aspects of these, aspects of hemoglobin oxygenation, and kinetics of CO2 transport and exchange. The 10 research units are supported by seven shared core facilities. It is expected that this unusually broadly based program will be effective in promoting increased collaboration between departments outside the School of Medicine and those within it with the ultimate goal of a better understanding of the physiological basis of pulmonary disease.